This invention relates to fluid control, and in particular to a variable differential adjustor for a fluid pressure-actuated switch, with the fluid, in the preferred form, being air.
In dwellings and other structures using sump pumps to drain subterranean building footings and avoid ingress of water into the structure, it is important that the sump pump be actuated when water removal limits occur. Thus, sump pumps have switches that are activated by many different types of actuation devices, such as floats, pressure pads and pressure tubes. It is the latter type of structure that is utilized with the invention of the present application.
Pressure tubes typically extend into a sump pit or other water collection area, and as water rises in the sump pit, pressure within the tube increases until a pressure-actuated switch is closed, thus activating the sump pump. Once the water level is reduced below a certain level by the sump pump, the pressure-actuated switch is deactivated, and pumping ceases. To control the level at which pumping begins, typically the tube is repositioned up or down, which then translates into a higher or lower water level which commences actuation of the sump pump. If repositioning of the pressure tube is impossible or inconvenient, then the only manner in which to change the actuation of a pressure-actuated switch would be to restrict air pressure to the switch, effectively delaying actuation or deactivation of the switch.
One form of such a delay is disclosed in U.S. Pat. No. 7,084,363, the disclosure of which is incorporated herein by reference. In the device of the '363 patent, a restrictor is provided having a restrictor housing with a fluid passage in which a restrictor plug, typically a set screw, is engaged. By judicious adjustment of the position of the set screw, fluid flow to and from the pressure the pressure-actuated switch is controlled, controlling when the switch is activated to control activation and deactivation of the sump pump.